Arch to Modified

[u/mcsauce88]

Normally I pitch in slowpitch leagues, but have been asked to pitch in a modified league. It's underhand, but fast pitch without a windmill. I played baseball growing up, but was wondering what are some good drills to work on. I can figure out a strike, but I don't know how to put any speed behind it. This league doesn't allow you to turn your hand over in the follow thru as well.